[LeetCode] Add Two Numbers 两个数字相加

问题描述

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

问题分析

该问题类似于如何使用链表实现加法的运算，按照数学计算的思路从个位数开始相加，设置一个变量来标记是否需要进位（需要进位的+1，不需要的加0），那么只需要在后一位的计算时加上进位即可。当相加的两个元素位数不同时，补零代替。

C++实现

class sloution{
    public:
    ListNode * TwoNumberPluss(ListNode *l1,ListNode *l2)
    {
        ListNode *res = new ListNode(-1);
        ListNode *cur = res;

        int carry = 0;
        while(l1||l2)
        {
            int n1 = l1? l1->val : 0;
            int n2 = l2? l2->val : 0;
            sum = n1 + n2 + carry;
            carry = sum /10;
            cur->next = new ListNode(sum%10);
            cur = cur->next;
            if(l1) l1 = l1->next;
            if(l2) l2 = l2->next;
        }
        if(carry) cur->next = new ListNode(1);
        return res->next;
    }

}